This invention relates to a high temperature seal of the kind which is used to close off reactors and vessels under high temperature conditions at their inlets or outlets.
In such a seal a closure member such as a cone or bell is caused to move relatively to an annular seat. If the material passing through is hot and abrasive the sealing edges of the cone and seat can wear away unacceptably fast. It has therefore been proposed to make the sealing edges of a hard metal such as cobalt cemented tungsten carbide. However, unless it is solidly supported at all times, a hard metal body easily spalls and cracks under impact forces such as would arise during the forcible closure of a cone on a seat.
Hard metal and steels from which reactor vessels are usually made have different coefficients of expansion, steel expanding more than hard metal. The result is that a ring of hard metal fitted on an inwardly facing shoulder tends to become loose as the temperature goes up, and closure impact on the ring could thus cause it to break.